The art is replete in many areas of electron beam generation with various types of heated filament electron beam sources of varied configurations. Single filament guns are described, for example, in U.S. Pat. Nos. 3,702,412 and 4,100,450 of common assignee herewith, and are embodied in Energy Sciences Inc., Type ESI Gun apparatus. Multi, including parallel, filament constructions have also been proposed as in, for example, U.S. Pat. No. 3,749,967 and U.S. Pat. No. 3,863,163.
Among the typical problems due to complexity with existing multi-filament guns are: high cost, severe difficulties in alignment, relatively low efficiency and difficult maintenance. Among the typical problems with existing single filament guns is the difficulty in obtaining cross beam uniformity over large dynamic range (40:1) in very long guns.
The problem of providing an efficient, simple and reliable construction that improves uniformity of extremely wide web width (say 10 feet or more), as well as a modular construction that can ease the maintenance, has still lingered in the art.